The present invention relates to Global Navigation Satellite System (GNSS) receivers, and more particularly, to methods and apparatus for compensating a clock bias in a GNSS receiver.
One of the most important issues related to GNSS receivers is how to obtain accurate GNSS time when a GNSS receiver enters a start up mode from a power-off mode. Typically, within the GNSS receiver, all components except a real time clock (RTC) are powered down in the power-off mode. According to the related art, a common way to get an initial GNSS time when the GNSS receiver is powered on is by reading the RTC time provided by the RTC as the Coordinated Universal Time, which is typically referred to as the UTC time, and by further converting the UTC time derived from the RTC time into a rough initial value of the GNSS time directly.
Please note that the RTC is a temperature sensitive component with an RTC drift value that may change severely with respect to temperature, where an accumulated amount from the RTC drift value with respect to time can be referred to as the RTC bias value. As time goes by during a power-off period of the GNSS receiver, the RTC drift value accumulates and the RTC bias value becomes greater and greater, causing the aforementioned initial value of the GNSS time to be inaccurate.